Mitigating GNSS Measurement Errors in Suspended Aircraft Tests for Efficient INS/GNSS Integration

Biju VS, Vinoj VS, Anand Shankar OT, Mohammed Basim A, Krishan Kumar, Biju V. Gopal, Rekha AR, Radhakrishna Pillai C, Padmakumar ES

Peer Reviewed

Abstract:	Global Navigation Satellite System (GNSS) receivers have become a critical component for precise navigation in modern aircraft. This paper investigates the challenges of using GNSS data in a Reusable Launch Vehicle (RLV) during field trials and missions, where the vehicle transitions from a vertical launch configuration to an aircraft-like descent. The RLV is equipped with dual GNSS antennas and an onboard Inertial Navigation System (INS), with navigation outputs generated using a 15- state extended Kalman filter that fuses GNSS and INS data. During autonomous runway landing tests, the RLV was airlifted by a helicopter and released at a predefined point to evaluate navigation accuracy. Performance analysis revealed significant velocity errors exceeding acceptable limits. The study identified three major sources of error: lever arm effects due to rotational motion, helicopter rotor-induced vibrations, and interpolation errors from high-frequency GNSS velocity variations. To address these challenges, novel techniques were developed, including compensating for lever arm effects by projecting relative antenna velocities to the satellite line-of-sight and applying corrections at the delta range level. A Butterworth band-stop filter was implemented to mitigate rotor-induced vibrations, and the GNSS measurement frequency was increased from 1 Hz to 10 Hz to reduce interpolation errors. Results demonstrate that these techniques reduced velocity errors from 0.24 m/s to below 0.08 m/s. The effectiveness of the proposed methods was validated through multiple helicopter sorties. This work provides a comprehensive framework for mitigating GNSS measurement errors in agile aircraft and offers practical insights for improving navigation performance during field tests and missions. Index Terms—GNSS, RLV, Aircraft test, Integrated navigation
Published in:	2025 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 28 - 1, 2025 Salt Lake Marriott Downtown at City Creek Salt Lake City, UT
Pages:	546 - 554
Cite this article:	VS, Biju, VS, Vinoj, OT, Anand Shankar, A, Mohammed Basim, Kumar, Krishan, Gopal, Biju V., AR, Rekha, C, Radhakrishna Pillai, ES, Padmakumar, "Mitigating GNSS Measurement Errors in Suspended Aircraft Tests for Efficient INS/GNSS Integration," 2025 IEEE/ION Position, Location and Navigation Symposium (PLANS), Salt Lake City, UT, April 2025, pp. 546-554.
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